Method of solid fuel combustion intensification

ABSTRACT

The substance of the invention consists in the combustion of the fuel-air mixture in the electric field by means of the catalyst located in the combustion zone and to which high voltage is applied, which results in reduction of activation energies of all endothermic combustion phases due to the formation of oxygen atoms, carbon radicals and oxygen-containing radicals. 
     Technical result: introduction of the catalyst in the combustion zone minimizes energy expenditure for creation of the low-temperature plasma, allows to increase the temperature in the combustion zone, to reduce activation energy of all endothermic processes taking place at the initial phase of combustion and to reduce carbon content in the ash and to achieve considerable fuel economy.

BACKGROUND OF THE INVENTION

The method relates to the power engineering, metallurgy, and namely, to the solid fuel combustion: coal, peat, wood.

The process of solid fuel combustion is well known. So far, a considerable number of methods of solid fuel intensification are known. One of the methods consists in combustion intensification by increasing oxygen concentration in the flame, resulting in increasing of atoms and oxygen-containing radicals in the combustion zone.

The method of oxygen-convector steel melting is known (see Kazakov N. F., Osokin A. M., Sishkova A. P. Technology of metals and other structural materials, 1975-688 p.). The substance of this method consists in the iron oxygen blow through the lance. During the high-temperature mass oxygen blowing oxidation of hardly oxidized additives is achieved. The highest oxidation of additives takes place at the oxygen jet-metal interface.

The disadvantages consist in the use of a precious oxidizer, unproductive oxidizer losses due to a large oxygen breakthrough, necessity of obtaining the oxidizer using additional complex and metal consuming technology.

The known from the literature method of intensification of the chemical catalytic heterophase processes by processing catalysis zone with the electric discharge (certificate of authorship No. 1036347, cl. B 01 D35/06/B 01 D 51/00.

Electrical filter Apr. 30, 1982, and Stolyarenko H. S. Mechanism of chemical radical reactions in heterophase ozone systems H₂O—O₃—O₂—Nox-SO₂//Bulletin of Cherkassy engineering-technology institute—No 3—1999—pp. 81-85). Influence of the electrical discharge on chemical heterophase processes results in the possibility of reactions taking place at temperatures 300 to 500 degrees lower as compared without the influence, which is explained by an additional electron, wave, light activation of process in addition to the temperature activation.

The disadvantages are that the technology was studied at low concentrations of the reacting components which leads to increase of expenditure of energy for generation of the electric discharge.

“Method of flame intensification and control” (Pat. No. 2125682 Russia, MKI F 23 No. 005/00 F 236005/00) was chosen as a prototype.

The method of combustion intensification consists in processing the flame with a strong longitudinal electric field (2 kV/cv and more) and a strong transversal electric field rotated, for instance, by means of a three-phase electrode system and a three-phase high-voltage source. The method comprises also operation of the flame height measurement and its other parameters, change of the interelectrode distance of the longitudinal field application to the flame with the simultaneous field intensity control. The method allows also to rotate the flame by the transversal electric field which increases the mixing and fuel-air reduction degree and additionally enhances the combustion. The proposed new operation of electrostatic fuel introduction in the combustion zone by the longitudinal electric field to the molecular level additionally enhances the flame combustion process and decreases fuel consumption. The method allows also to control the flame geometry, temperature and heat conduction thereof by the variation of geometry and electric parameters of the above said electric fields, for instance, to focus the flame which is sufficient, for instance, for heat treatment of metals and alloys.

The disadvantages are high specific power inputs decreasing power efficiency of the process, necessity of fuel mixing and electrostatic atomization, complexity of combustion process regulation.

The invention is aimed to add to the thermal component of the combustion process activation an electron, wave, light, electrocatalytic activation in order to achieve maximum degree of carbon burning from the solid fuel.

SUMMARY OF THE INVENTION

The essence of the invention is based on the in the fuel-air mixture combustion in the electric field by means of a catalyst located in the combustion zone to which a high voltage is applied, resulting in decrease of activation energies of all endothermic phases of combustion due to creation of oxygen atoms, carbon radicals and oxygen-containing radicals.

The aim is achieved by overlapping discharge zone, combustion zone and electron-catalytic processes of the synthesis of the low-temperature plasma generated between two electrodes by applying high voltage to the electrodes, the electrodes being made of variable valency metals or their oxides, or other conductive material with the catalyst applied. The voltage at the electrodes is within 5 to 20 kV.

The comparative analysis with the prototype allows making a conclusion that the claimed solution differs from the prototype by the creation of the low-temperature plasma and electrocatalytic processes in the combustion zone. This leads to the approach of speeds of thermodestruction and electrocatalytic destruction of carbon and hydrocarbons which are desorbed from the coal; to the increase of the rates of oxidation of the carbon-bearing compounds to the carbon dioxide and water, owing to a high concentration of oxygen-containing radicals, to the increase of the carbon burning degree from the solid fuel and economy of the solid fuel. As the catalytic plasma and oxidation processes are brought in one zone, compared to the prototype the energy expenditures are decreased by three orders, which allows achieving a high specific economy of fuel. The fuel expenditures for creation of low-temperature plasma do not exceed 2 to 5% of the energy effect obtained according to the proposed method.

The method of combustion consists in the following.

The method by its essence is composed of the physical and thermochemical phases. Fuel grinding, fuel and air transport to the combustion zone, fuel and air mixing and combustion in the combustion chamber of different design are made. Intensification of the combustion process according to the prototype using the electric field relates to the mixing and combustion zone. Intensification of the claimed method relates to the combustion zone where combustion processes, oxidation radical processes, fuel catalytic activation are brought together.

BRIEF DESCRIPTION OF THE DRAWINGS

The proposed technical solution is explained by the drawings:

FIG. 1—installation diagram;

FIG. 2—comparative dependence of the temperature variation of the heat-transfer medium.

The flowchart of the FIG. 1 comprises: 1—combustion chamber; 2—fuel combustion zone; 3—electrothermal ignition tube of the fuel-air mixture; 4—reservoir with heated water; 5—bottom grate; 6—thermostatic insulation; 7—high-voltage electrode; 8—power supply; 9—ground.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The air flow containing pulverized solid fuel comes into the combustion chamber 1. It passes through the grid 7, bottom grate 5, and arrives into the zone 2. Electric ignition 3 provides the ignition temperature of the fuel-air mixture and after that it is switched off. The stationary combustion process is established which is defined by the heating rate of the precisely measured volume of the heat-transfer medium 4 (water in our case). The 5 to 20 kV voltage is supplied from the power supply 8, 9 to the grid 7 coated with the catalyst enhancing the combustion process. This mode is defined by the heating rate of the equal volume of the heat-transfer medium.

FIG. 2 shows dependence of the water temperature variation from the time when carrying out idle experiment and with the discharge. When coal is combusted with the discharge water heating is accelerated which is evidence of the release of a larger amount of heat as compared to the idle experiment. (On the curves shown three zones can be seen: A—zone of establishment of the uniform combustion process (beginning of curves from 0 to 2 minutes); B—zone of uniform coal combustion: rectilinear section in the middle of the curve, from 2 to 16 minutes; and zone C—extinction of the combustion process (after 16 minutes). For calculations of the coal combustion power and efficiency of the electric activation is used the section of the uniform combustion.

The specific power of heat release in the idle experiment is 73 W/h, while in case of the discharge it averages 94.5 W/h, which is 18.6% higher, and, in its turn, reduces fuel expenditure by the same amount.

During two experiments the rate of coal burning was defined. For this purpose, the coal ash and the rate of coal burning with and without the discharge was measured. The coal burning rate in the idle experiment is approximately 72% (which approximately corresponds to boilers with the integral grate); the coal burning rate with the use of the discharge amounts to 89%. The rate of burning increase was 17.45% on average.

When the catalytic grid of the high voltage electrode is removed from the combustion zone, the heat-carrier medium heat rates are approached and the intensification effect of the fuel combustion is decreased and the carbon content in the ash is near the values obtained in the idle experiment.

Thus, the proposed method of the combustion process intensification leads to the fuel economy, more complete burning out of the solid fuel and increase of the combustion process efficiency.

The technical solution claimed allows create an installation for solid fuel combustion intensification for existing boilers of any capacity. Implementation of the technical solution needs not modifications or reworking of the boiler furnaces; electric equipment for creation of electric discharge and low-temperature plasma is standard; catalysts sprayed on the high voltage grid are publicly available.

The experimental model in the form of the test bed installation is manufactured and tested by the applicants. 

1. A Method of solid fuel combustion intensification consisting in the combustion of the air-fuel mixture in the electric field, characterized in that the combustion process is taking place by means of a catalyst located in the combustion zone and to which a high voltage is applied, resulting in the reduction of activation energies of all endothermic combustion phases due to the formation of oxygen atoms, carbon radicals and oxygen-containing radicals.
 2. The method according to claim 1 characterized in that the electrodes are made of metals of variable valency, of their oxides or any other conductive material with the application of the catalyst.
 3. The method according to claim 1 characterized in that the voltage applied to the electrodes is within 5 to 20 kV. 